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214                                 Gauges.

depth being rounded off at top and at bottom, and the angle being
55°. The rounding at the bottom is given by the tool in Fig. 224,
but that at the top, as well as the general finish, is obtained by
hand-chasing tools. These are seen at Fig. 226, where A is for
the spindle, and B is for chasing the nut; the first being held
transversely and the second longitudinally. They are both
carefully cut to correct section of thread. (See App. //,/» 815.)

Fixing a Stud.—Studs are used in places where bolts are
inadmissible, because the material cannot be drilled right through.
The stud hole being drilled and tapped, and the stud having been
turned and screwed so as to fit tightly in the stud hole, the former
is entered, and a stud box placed upon the opposite end, as in
Fig. 227. Outwardly this tool has the appearance of the box
key described on page 113; but is screwed internally to fit the
stud, and has a small plate of copper at the bottom of the
socket to avoid damaging the work. A wrench being applied
to the square, the whole is advanced until "stopped by the
plain portion on the stud, when the box may be removed by
a sharp back turn.

Cylindrical Gauges are of great value in securing accurate
work. They are shewn at Fig. 2270. B being termed a * plug/

and A a ' ringJ gauge. The first is used for testing the accuracy
of a socket, and the second that of a pin, and both are made to
such perfection that the tested pin would be found to fit in its
socket freely, but with no appreciable shake. There are cases
where the ring gauge cannot be applied, and then the 'horseshoe/